(a) The field of the invention
The present invention relates to a nozzle for the texturization of yarns.
By "texturization" is meant, as is known, an operation whereby particular conformation characteristics are imparted to the yarn, to which correspond desired mechanical characteristics: e.g. a crimp to a certain degree and of a certain type which confers a desirable elasticity to yarns made of filaments, in particular synthetic filaments.
(b) The state of the art
It is known to effect such texturization by pneumatic means, particularly by subjecting the yarn to the action of a compressed air jet in a device which is usually called and will be called herein "nozzle", which operates essentially on the principle of a Venturi cone, the yarn being fed to a central passage and the compressed air to a channel which concentrically encompasses it, the air and the entrained yarn passing thereafter through a passage shaped like a Venturi cone, whereby the compressed air entrains the yarn and subjects it to a mechanical action, generally based on the turbulence of the air in the zone of the cone, which produces the desired conformation modifications of the yarn.
U.S. Pat. No. 3,545,057, U.S. Pat. No. 3,863,309, and copending Italian patent application No. 26178 A/74 may be cited among the patents relating to texturization nozzles.
Generally such devices are constituted essentially by three main parts, viz.: a body having a cylindrical cavity constituted by cylindrical parts of different diameters: a so-called "needle" which is inserted in a cavity of the body and has an axial through bore, which may have in its terminal portion a zone or "orifice" having a smaller diameter, the needle generally ending in an outwardly frusto-conical head; and a closure element which will be called herein "plug", which has an axial biconical passage constituted by two generally frusto-conical parts, the first part having a converging and the second a diverging taper (in the direction of the yarn travel), such plug being mounted on the body in such a way as to face with its convergent taper the frusto-conical part of the nozzle head, means being provided for feeding compressed air to the inside of the body and between it and the needle, in such a way that the air may flow out through the biconical passage (Venturi cone) of the plug, entraining therewith the yarn which comes from the axial bore of the needle.
A number of known nozzles of this kind are more or less adapted to produce a texturization effect on the yarn, but their efficiency is not quite satisfactory and for this reason the art has been endeavouring for some time to modify and perfect them to obtain therefrom an improved efficiency. Various proposals have been made to this end; and in particular, e.g., it has been proposed in U.S. Pat. No. 3,863,309 hereinbefore cited, to define on the terminal part of the needle and about the outlet of its axial bore, a frusto-conical cavity having a taper opposed to that of the outer surface of the needle head, for the purpose of creating at the point at which the yarn comes out of the needle, a chamber wherein the air may have turbulences which, according to such patent, improve the efficiency of the nozzle.
In spite of all this, all known nozzles, including the most improved ones, have the common drawback of a high consumption of compressed air, which substantially affects the economy of the process. The precise reasons of such an excessive consumption are not clear, and even though applicants will set forth a hypothesis regarding it, they do not wish to be bound to its accuracy, the only relevant fact being that the compressed air consumption is actually high and that it is desirable to reduce it. This phenomenon is particularly evident when a yarn is produced that will be called hereinafter "binary yarn", viz. a yarn made of two components which are fed with different speeds or more precisely with different overfeeds, so that the final yarn is composed of two coupled yarns having different lengths in an extended condition, one of which therefore has significantly more marked deformations, crimps and bends than the other.
It is an object of the present invention to provide a nozzle for the texturization of yarns, of the Venturi cone type, wherein the compressed air consumption is significantly reduced, for a given production, with respect to all known devices.
It is a further object of the present invention to provide a device of the above type which can be regulated precisely and easily.
It is a further object of the invention to provide a device of the above type which is adapted to the production of binary yarns in a wide range of counts.
It is a further object of the present invention to provide a device of the above type which is economical, simple, and reliable in operation.